FLYING MACHINES. 
3 
than the stag-beetle, possesses 5 times more relative surface, 
&c. It is the same with birds. The sparrow which weighs 
about ten times less than the pigeon, has twice as much relative 
surface. The pigeon which weighs about eight times less than 
the stork, has twice as much relative surface. The sparrow 
which weighs 339 less than the Australian crane, possesses seven 
times more relative surface, &c. If we now compare the insects 
and the birds, the gradation will become even much more strik- 
ing. The gnat, for example, which weighs 97,000 times less 
than the pigeon, has 40 times more relative surface ; it weighs 
3,000,000 times less than the crane of Australia, and possesses 
relatively 140 times more surface than this latter, which is the 
heaviest bird the author had weighed, and it was that which had 
the smallest amount of surface, the weight being 20 lbs. 15 oz. 
2 J dr. avoirdupois, and the surface (referred to the kilogramme 
2 lbs. 3*27 oz.) 139 square inches; yet of all travelling birds, 
they undertake the longest and most remote journeys, and, with 
the exception of the eagle, elevate themselves highest, and main- 
tain flight the longest. 
M. de Lucy remarks, that if the law of surface in inverse 
ratio to weight be regarded, the cause of all the errors which 
have been committed will be readily understood ; for a mathe- 
matician who should select as his type an excellent bird of flight 
such as the swallow, by ascertaining its weight and surface, 
will apportion nearly one mtee or 1,550 sq. in. to the kilo- 
gramme, and consequently 75 mtoes for a man of 75 kilo- 
grammes, that is to say, about 165 lbs. would require a surface 
of 116,250 sq. in. Should he select the pigeon, he will arrive 
at a result quite different, because the pigeon being heavier than 
the swallow has a surface relatively smaller. According to this 
type, he would arrive at the conclusion that only 20 m^res of 
surface or 31,000 sq. in. would be requisite for a man of the 
same weight. 
With regard to the crane of Australia, the weight of one of 
which was 20 lbs. 15 oz. 2i dr. avoir., possessing a surface of 
only 1,324 sq. in., this third example would give to a man of 
the before-named weight a surface of no more than 10,850 
sq. in. 
Again, should he select a type amongst insects, for example 
the blue dragon-fly whose flight is so rapid, he would discover 
the weight to be rather more than J grain, and surface nearly f 
of a square inch, which referred to the selected standard of com- 
parison would give 9,416 sq. in. and for the man 705,800 sq. in. 
Were we to determine the amount of sustaining surface re- 
quisite for the man from some of the butterfly tribe, whose 
wings are so prodigiously expanded in comparison with their 
weight, we should arrive at results so much in excess of these 
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